— _____
— It's an apartment building.
A:What's your home?
B:Where's your house?
C:What kind of house do you live in?
D:Where's the home?
某同学选用如下图片进行研究性学习。那么应确定的研究主题是( )
若a→+b→=a→-b→=2a→,则向量a→+b→与a→的夹角为( )
In the writer’s opinion, students can’t remember words because _______.